I just wanted to see if anyone had any information on a P0420 code and wanted to see what the most likely causes were for this model year. Thank you all.

 

P0420 'Catalyst below threshold efficiency'

This simply means the rear O2 is picking up fluctuations in the output gases, indicating the catalyst is not properly working.

This does not mean the catalyst itself is faulty.
If the engine is running to rich or lean the catalyst cannot function properly.
If there is a misfire, the catalyst cannot function properly.
If the engine is out of tune/needs a tuneup, the catalyst cannot function properly.

And sometimes it may just be a code caused by a temporary fault due an uncommon event while driving.

If there are no other codes, clear the code via pulling the fuse, do not use a code reader to 'clear' the code as you want to see if the code will reappear and not just lingering.

Often times when a vehicle has been driven for a long time with no interruption in PCM memory(being cleared) it will gradually adjust parameters to keep the vehicle running smoothly. Once it gets to a point where it has maxed out certain parameters, but they are still within acceptable range, the engine may not run as efficiently as it should. With the P0420 code it can demonstrate that although the car is running fine it is out of tune to not have the catalyst work properly. Thus 'below threshold efficiency' code may pop up.

When clearing the code and going for a drive do not be surprised if the CEL comes back on with a different code or multiple codes. These will be indicative of what the real problem is, if there indeed is one.